Information (data) is broken into [[/​doc/​howto/​packet.scheduler/​packet.scheduler.theory#​packets|packets]] prior to being transported to their destination(s).

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**Example:​**\\

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* [[wp>​Ethernet]] (see [[wp>​IEEE 802]] for even more standards) is a huge and successful family of modular //​communication protocols//,​ [[wp>​Fast Ethernet]] comprises the ones that have a gross throughput ([[wp>​Data signaling rate]]) of 100MBit/s and [[wp>​100BASE-TX]] is one distinct example, one specific standard.

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* [[wp>​Ethernet frame]] is the denomination for data chunk, a packet transmitted over Ethernet. This is common for all Ethernet standards, whereas the cabling, the encoding and other stuff is not. Depending on the wiring [[wp>​Carrier sense multiple access with collision detection|CSMA/​CD]] could be avoided.

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* //As you can see, this layer, has very technical aspects, and also some theoretical,​ logical or software aspects.//

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==== ... is layer based ====

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The [[wp>OSI model]] outlines the various layers that data must traverse on it's journey from its source to its destination(s).

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Each layer has it's own set of rules (protocols) for handling data packets and adds or removes it's own header (and sometimes a footer) before passing data packets to the next layer. It treats each packet, with or without formatting from other layers, as a simple payload, ignoring it's contents. ​ This process is referred to as [[wp>​Encapsulation_(networking)|encapsulation]].

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The software and hardware associated with each individual layer is not concerned with, and in fact, not even aware of what happens to the packets in the other layers. ​ It's only function is to format the packets it receives from the layer above or below in a predictable fashion. ​ In this way a very complex process is broken down into a series of simple steps which allows all kinds of different technologies to simply and reliably interact with one another. ​

The //physical layer// always concerns itself with the medium the signal traverses through (or over) while the //link layer// could be split into two sub-layers: //​[[wp>​Media Access Control]]// and //​[[wp>​Logical Link Control]]//​. ​ The [[wp>​Media Independent Interface]] is again something different, this is used to connect the distinct switch-chip to the SoC.

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How big a packet is, and how it's header looks like depends on the protocol or standard it abides by. Read about this: , [[wp>IP packet]], for an overview. For real precise technical data, read the corresponding RFCs.

Please note, that the Ethernet protocol family comprises standards of Layer 2 and also Layer 1. The latter are e.g. 100Base-TX or 1000Base-T. [[wp>​Point-to-Point Protocol over Ethernet|PPPoE]] is yet another Layer 2 communication protocol! And DSL is another Layer 1 communication protocol. So the Modem on the customers side communicates over some DSL-protocol with the [[wp>​DSLAM]] on the ISP side and the router communicates with the [[wp>​Broadband Remote Access Server|DSL-AC]] over PPPoE.

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Being Layer 1 protocols, 1000Base-T or DSL don't care about packets or whatever. Their logic is only concerned with transmitting the data over the specified medium.